Blasting-explosive assembly



Dec. 16, 1930. c PRATT 1,785,529

BLASTING EXPLOSIVE ASSEMBLY Filed Jan. 10, 19 30 Jmnnl ot CarZD. Praia.

ddogm 1 Patented Dec. 16, 1930 UNITED STATES PATENT OFFICE CARL D. PRATT, OF TAMAQUA, PENNSYLVANIA, ASSIGNOR TO ATLAS POWDER COM- PANY, OF WILMINGTON, DELAWARE, A CORPORATION OF DELAWARE BLASTING-EXPLO SIVE ASSEMBLY Application filed January 10, 1930. Serial No. 420,013.

My invention relates to improvements in blasting explosive assemblies, and it has for its object to provide a group of new and highly useful commercial blasting explosives which will have essentially the spreading and far-reaching character of action of ordinary black blasting powder, but with much more powerful effects than ordinary black blasting powder. These more powerful effects are produced by employing a fairly continuous core or train of high explosive composition, within a charge of blasting powder composition, in such a manner that the speed of reaction of the blasting powder is uniformly and greatly increased and also that considerable amounts of heat and gas volume are added to its reaction.

For many years, ordinary black blasting powders have been extensively used in loos ening and dislodging heavy burdens of rock and debris so that large mechanical shovels can handle them. This type of work is chiefly involved at such operations as quarries, open-pit mines, railroad cuts, large canals, etc. The outstanding advantages of blasting powder compositions. for this type of work. are their low cost and their spreading action br effectiveness over comparatively large volumes of blasted burden. This is in contrast to the tendency of a high ex- )losive toward greater pulverization of the blasted material Within more limited volumes.

The low strength and poor water resistance of blasting powder are, however, distinct disadvantages for this type of work. The low strength of blasting powder makes it necessary, except Where very light burdens are experienced, to concentrate the charges in pockets made by springing or chambering the bore-holes with preliminary charges of high explosives. This chambering process not only involves the cost of the high explosive employed, but also causes much delay; it being necessary to allow the bore-holes to cool before loading with the final charges of blasting powder. in addition, it is often necessary, on account of low strength. to ignite the blasting powder charges by means of detonating fuse, such as Cordeau, which increases its effectiveness by speeding up the decomposition of the charges without actually adding appreciable amounts of energy thereto. Further, because of low strength, it is impractical to pack ordinary blasting powder compositions in waterproof containers or cartridges, for use in wet bore-holes, because it then cannot be loaded to sufficiently high charging density-especially within chambered pockets to perform the desired work. This makes it necessary to substitute more water resistant, but more expensive high explosives for blasting powder, wherever wet bore-holes are encountered.

With the foregoing facts in mind, it has been my aim to provide a blasting explosive assembly, which will be materially stronger and faster than ordinary blasting powder composition, but with a minimum departure from its character of action, to permit its being used in non-chambered boreholes, without Cordeau, and whose water resistance will be so improved especially when packed in waterproof containersthat it may be used in wet as well as dry boreholes.

I have discovered that the above aims may be reached by using a high explosive core, running longitudinally through compressed or pelleted charges of black blasting powder; the said high explosive core being of such magnitude that it greatly increases the actual strength of the blasting powder, through the addition of the greater amounts of heat and gas volume resulting, and having a sufficiently high velocity that the deflagration speed of the blasting powder is sufficiently increased, without the use of Cordeau.

In fact, I have found that by varying the strength, velocity, density and proportion of the high explosive core used in my new assembly, I may attain even more ideal effectiveness for various types of burden, than may be obtained with Cordeau-blasting powder charges. This is because the velocity of (ordeau is practically constant at about 5000 IlHttlS. per second and because the strengths of blasting powder composition vary over a very narrow range, whereas my new explosive assemblies provide velocities ranging from about 2500 meters per second to about 6500 meters per second and actual strengths amounting to as much as about five or six times that of ordinary black blasting powder.

I prefer the use of compressed or pelleted charges of blasting powder composition, in my new type of explosive assembly, for several reasons. For example, first, the blasting powder charges may be brought to maximum charging density, in the pellet form. This enables the best possible concentration of the blasting powders energy. Second, blasting powder is more water resistant in the pellet than in the granular form; it being more diflicult for water to penetrate into the interior of a black powder pellet than into a charge of grain powder. Further, the pellets, themselves, may be coated with a protective coating of wax, even before being assembled into cartridges. Third, pelleted powder makes a more rigid cartridge than grained powder. This makes the cartridges easier to assemble at the mill, less apt to burst open during shipment, handling and loading and facilitates charging into bore-holes,the cartridges having less chance of being misshapen.

A primary requisite of my invention is that the said high explosive core must have such propagation sensitiveness to detonation when initiated by a high explosive primer that it will detonate completely throughout required lengths of charges; even when formed by two or more cartridges loaded end to end in bore-holes. This is necessary in order to ensure uniformity of action throughout the entire lengths of the charges.

' More specifically, I prefer the use of a high explosive core, having high strength and velocity of detonation, in order to attain the effectiveness necessary for average blasting conditions. It will be readily seen, however, that the character of the action of such an assembly may be varied over a considerable range, through variations in the strength, velocity, density and proportion of high explosive core usedwithout being outside the scope of my invention.

I further specify that the explosive or composition used to surround the said high explosive core shall be of the defiagrating type as contrasted to high explosive compounds or compositions which are sensitive to detonation. This specification is essential to my invention, as I desire to retain as much of the action of a low or defiagrating explosive as possible; the hard-hitting blow of the high explosive core being cushioned and absorbed by the deflagrating explosive surrounding it, whose decomposition takes the form of a very rapid combustion rather than the almost instantaneous disintegration or detonation of a so-called high explosive. In other words, it should be clearly understood that the scope of my invention does not include the use of a surrounding material or composition, which may be classified as a high explosive; it being common practice to use priming charges for such types of high explosives having poor sensitiveness, in order to ensure their com plete detonation.

The higli explosive cores, used in my new blasting assemblies, preferably have a minimum diameter of approximately three fourths of one inch. This is necessary to my invention, in order to assure the complete propagation of the detonation of the cores used in my new type of assembly.

I also prefer that the said high explosive cores be centrally located in the assemblies, in order that they may be completely and uni formly surrounded with the non-high explosive main charge and also facilitate the loading of two or more cartridges, as in a bore-hole, so as to have their respective cores in position for an unbroken wave of detonation to propagate successively, through the several cores, along the entire length of the charge. It should be understood, however, that the use of cores, which are not exactly centrally located, are still within the scope of my invention, provided the complete detonation of the employed core is attained.

Furthermore, I specify that the high explosive core shall comprise no less than 2% and no more than 50% of the total weight of the assembly. At least 2% of high explosive core (by weight) is necessary to my inven-. tion, in order to provide an appreciable increase in the strength effectiveness of my new assembly as compared with straight charges of blasting powder. On the other hand, it is necessary that no more than about 50% of high explosive core (by weight) shall be used, in order to retain the characteristic action of a low explosive.

The novel and advantageous features of my improved explosive, over all other known blasting explosive assemblies, for certain types of work, are evident, as for instance in quarries, open-pit mines, railroad cuts, large canals and the like. For this type of work, it has many advantages over what has heretofore been considered the most ideal explosive assembly, namely; the use of detonating fuse, such as Cordeau, in conjunction with black blasting powder charges. Vvhereas, detonating fuse adds to the effectiveness of a blasting powder charge by merely providing a more rapid ignition without adding appreciably to the actual explosive strength, my invention provides a much greater and more ideal effectiveness by imparting a. very appreciable increase in actual explosive strength in addition to a speed of ignition which may be greater, less or the same as with the use of a detonating fuse, such as Cordeau; depending on what speed of ignition is found to be most ideal for the particular burden involved. At the same time, my explosive provides this more ideal effectiveness, without the necessity of chambering the bore-holes or of avoiding its use when wet bore-holes are encountered.

Examples of my new type of blasting explosive assemblies are, as follows:

1. \Vaterproofed cartridges, four and onehalf inches in diameter by eighteen inches long, over all, consisting of a central core of L. F. nitroglycerine dynamite, 1 inches in diameter by 18 inches long, the said core being enclosed in a paper shell and inserted through the central openings of pellets of B black blasting powder; the said pellets being cylindrical in shape, each having an outside diameter of 4 inches, 1 inch diameter central openings, and 2 inches long. For cartridges, 18 inches in length, 'nine of such pellets would be required.

2. Waterproofed cartridges, four inches in diameter by sixteen inches long, over all, consisting of centrally located cores of 50% L. F. nitroglycerine dynamite enclosed in paper shells, 1 inches diameter by 16 inches long, surrounded by main charges of granular B black blasting powder.

In the accompanying drawings I have illustrated a cartridge like that described in Example #1 above, wherein 5 designates the pellets of black blasting powder or equivalent low explosive and 6 the cores of high explosive extending therethrough, said cores being preferably enclosed in the paper shells 7. Any desired number of the pellets may be employed though I have shown an 18 inch cartridge, using nine of the pellets, the whole being formed into a cartridge by encasing the same in any suitable form of wrapper 8 such as waterproofed paper, rubberized cloth or other suitable material.

It should be understood that the above are merely examples of a large variety of assemblies which may be derived from my invention and that I do not limit myself as to the character, shape or composition of either the high explosive core or the surrounding, nonhigh explosive material comprising my assembly, providing they fulfill the specifications set forth above. For instance, I may desire to use a low velocity, high strength, high explosive core or I may desire to use a defiagrating, surrounding charge, such as ground wood meal, impregnated with an inorganic oxygen carrier, etc.

Summarizing, my improved explosive assembly consists of a core of any suitable high explosive (preferably of high strength, velocity and sensitiveness), surrounding which is a main charge consisting of any suitable deflagrating but non-high explosive composition (preferably B black blasting powder). The assembly may be in the form of an unbroken train of high explosive core, so suspended in a bore hole that the loose main charge may be loaded around it or it may consist of cartridges, each of which contains a section of the high explosive core, so located that when two or more of these cartridges are placed end to end, as in a borehole, the high explosive core will essentially be a continuous train and whose detonation will propagate through as such. The high explosive core shall be no less than three fourths of one inch in diameter and it shall comprise no less than 2% and no more than 50% of the totalweight of the assembly.

If carried into etfect for blasting over-burdens, quarries, etc., my invention will not only be more convenient for this type of work, as hereinbefore described, but will also tend to greatly reduce the cost of such blasting.

Having described my invention, what I claim is:

1. An explosive assembly of the character described, consisting of av main charge of a deflagrating but non high explosive composition, in which is located, longitudinally, a core with a minimum diameter of inch, consisting of a high explosive composition comprising no less than 2% and no more than 50% of the total weight of the assembly and which core extends entirely through the main charge.

2. An explosive assembly of the character described, comprising a. cartridge consisting of a main charge of a deflagrating, but nonhigh explosive composition and a core with a minimum diameter of inch, consisting ot a high explosive composition comprising no less than 2% and no more than 50% of the total weight of the assemblyqthe said core being exposed at two faces of the main charge and being located so that the wave of detonation will propagate continuously and uniformly when two or more such cartridges are charged end to end, as in a bore-hole.

3. An explosive assembly of the character described, comprising a cartridge consisting of a main charge of pelleted blasting powder and a core with a minimum diameter of inch, consisting of dynamite comprising no less than 2% and no more than 50% of the total weight of the assembly; the said core extending entirely through the cartridge be- "ing located so that the wave of detonation will propagate continuously and uniformly when two or more such cartridges are charged end to end, as in a bore-hole.

4. An explosive assembly of the character described, consisting of a main charge of granular blasting powder, in which is located, longitudinally, a dynamite core with a minimum diameter of inch and comprising no less than 2% and no more than 50% of the total weight of the assembly. said core being exposed at two faces of the main charge.

5. An explosive assembly of the character described comprisin a cartridge having a minimum diameter 0 1.5 inches consisting of a main charge of a deflagrating, but nonhigh explosive composition and a core with a minimum diameter of .75 inches, consisting of a high explosive composition comprising no less than 2% and no more than 50% of the total Weight of the assembly; the said core being exposed at two faces of the main charge and being located so that the Wave of detonation will propagate continuously and uniformly when two or more such cartridges are charged end to end, as in a bore-hole.

6. An explosive assembly of the character described. consisting of a main charge oi defiagrating but non-high explosive composition, and a core of a high explosive composition in said main charge of such magnitude as to materially add to the heat and gas volume of the Whole, upon explosion said core being exposed at a face of the main charge.

7. An explosive assembly of the character described, consisting of a main charge of deflagrating but non-high explosive composition, and a core of a high explosive composition in said main charge, and extending entirely through said main charge and being exposed at the ends thereof, said core b ing of such magnitude as to materially ail 1 heat and gas volume of the Whoie upon explosio'n.

8. An explosive assembly of the described, consisting of a main ch deflag'rating but non-high explosiv tion having a substantially centr: core of a high explosive coniposizm ing longitudinally completely third and of such volume as to mate' the hea; and gas volume of the explosion,

5). fan exp t assembly n 1"(3192 descri Ew-Kl, mnsisting of a Ciil'tiii uprisiHfQf :1 iiirzil iy of pellets of a c hut non-l: compositi at three i e assensb i si'ibstrzntiaiiyra oth r so that the Wav *i=-;; ::gate continuim iormly throughout the length tridge. and wherein said cores in, magnitude in proportion to the magnitude of said pellets as to materially add to the heat and gas evolved upon the explosion of the whole.

In testimony whereof I affix my signature.

CARL D. PRATT. 

